package com.leon.datalink.core.persistence;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.concurrent.*;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicLong;
import java.util.concurrent.atomic.AtomicReference;
import java.util.Map;
import java.util.HashMap;
import java.util.List;
import java.util.ArrayList;
import java.util.Set;
import java.util.HashSet;
import java.util.Collections;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;

/**
 * 高可用性架构管理器
 * 
 * 提供企业级的高可用性功能，包括：
 * - 多活数据中心支持
 * - 自动故障转移机制
 * - 数据同步和一致性保证
 * - 灾难恢复和备份策略
 * 
 * @author DataLink Team
 * @version 1.0.0
 */
public class HighAvailabilityManager {
    
    private static final Logger logger = LoggerFactory.getLogger(HighAvailabilityManager.class);
    
    private static volatile HighAvailabilityManager instance;
    
    // 集群状态
    private final AtomicReference<ClusterState> clusterState = new AtomicReference<>(ClusterState.INITIALIZING);
    private final AtomicBoolean isPrimaryNode = new AtomicBoolean(false);
    private final AtomicLong lastHeartbeat = new AtomicLong(System.currentTimeMillis());
    
    // 节点管理
    private final Map<String, NodeInfo> clusterNodes = new ConcurrentHashMap<>();
    private final Set<String> activeNodes = Collections.synchronizedSet(new HashSet<>());
    private final AtomicReference<String> primaryNodeId = new AtomicReference<>();
    
    // 故障转移
    private final AtomicLong failoverCount = new AtomicLong(0);
    private final AtomicLong dataReplicationCount = new AtomicLong(0);
    private final AtomicLong backupOperations = new AtomicLong(0);
    
    // 执行器
    private final ScheduledExecutorService heartbeatExecutor;
    private final ScheduledExecutorService replicationExecutor;
    private final ExecutorService failoverExecutor;
    
    // 配置参数
    private volatile long heartbeatIntervalMs = 5000; // 5秒心跳
    private volatile long failoverTimeoutMs = 15000; // 15秒故障转移超时
    private volatile int replicationFactor = 3; // 数据复制因子
    private volatile long backupIntervalMs = 300000; // 5分钟备份间隔
    
    // 数据同步
    private final Map<String, ReplicationStatus> replicationStatus = new ConcurrentHashMap<>();
    private final List<BackupRecord> backupHistory = Collections.synchronizedList(new ArrayList<>());
    
    private HighAvailabilityManager() {
        this.heartbeatExecutor = Executors.newScheduledThreadPool(2,
            r -> {
                Thread t = new Thread(r, "ha-heartbeat-" + System.currentTimeMillis());
                t.setDaemon(true);
                return t;
            }
        );
        
        this.replicationExecutor = Executors.newScheduledThreadPool(3,
            r -> {
                Thread t = new Thread(r, "ha-replication-" + System.currentTimeMillis());
                t.setDaemon(true);
                return t;
            }
        );
        
        this.failoverExecutor = Executors.newFixedThreadPool(2,
            r -> {
                Thread t = new Thread(r, "ha-failover-" + System.currentTimeMillis());
                t.setDaemon(true);
                return t;
            }
        );
        
        initializeHighAvailability();
        logger.info("高可用性架构管理器初始化完成");
    }
    
    public static HighAvailabilityManager getInstance() {
        if (instance == null) {
            synchronized (HighAvailabilityManager.class) {
                if (instance == null) {
                    instance = new HighAvailabilityManager();
                }
            }
        }
        return instance;
    }
    
    /**
     * 初始化高可用性功能
     */
    private void initializeHighAvailability() {
        // 启动心跳检测
        heartbeatExecutor.scheduleAtFixedRate(this::sendHeartbeat, 0, heartbeatIntervalMs, TimeUnit.MILLISECONDS);
        heartbeatExecutor.scheduleAtFixedRate(this::checkNodeHealth, heartbeatIntervalMs, heartbeatIntervalMs, TimeUnit.MILLISECONDS);
        
        // 启动数据复制
        replicationExecutor.scheduleAtFixedRate(this::performDataReplication, 0, 10000, TimeUnit.MILLISECONDS);
        
        // 启动备份任务
        replicationExecutor.scheduleAtFixedRate(this::performBackup, backupIntervalMs, backupIntervalMs, TimeUnit.MILLISECONDS);
        
        // 初始化集群状态
        clusterState.set(ClusterState.ACTIVE);
        
        logger.info("高可用性服务已启动");
    }
    
    /**
     * 加入集群
     */
    public void joinCluster(String nodeId, String nodeAddress) {
        NodeInfo nodeInfo = new NodeInfo(nodeId, nodeAddress, System.currentTimeMillis(), NodeStatus.ACTIVE);
        clusterNodes.put(nodeId, nodeInfo);
        activeNodes.add(nodeId);
        
        // 如果是第一个节点，设为主节点
        if (primaryNodeId.get() == null) {
            primaryNodeId.set(nodeId);
            isPrimaryNode.set(nodeId.equals(getCurrentNodeId()));
        }
        
        logger.info("节点 {} 加入集群，地址: {}", nodeId, nodeAddress);
    }
    
    /**
     * 离开集群
     */
    public void leaveCluster(String nodeId) {
        NodeInfo nodeInfo = clusterNodes.get(nodeId);
        if (nodeInfo != null) {
            nodeInfo.setStatus(NodeStatus.LEAVING);
            activeNodes.remove(nodeId);
            
            // 如果是主节点离开，触发故障转移
            if (nodeId.equals(primaryNodeId.get())) {
                triggerFailover();
            }
            
            clusterNodes.remove(nodeId);
            logger.info("节点 {} 离开集群", nodeId);
        }
    }
    
    /**
     * 发送心跳
     */
    private void sendHeartbeat() {
        try {
            String currentNodeId = getCurrentNodeId();
            lastHeartbeat.set(System.currentTimeMillis());
            
            // 更新当前节点状态
            NodeInfo currentNode = clusterNodes.get(currentNodeId);
            if (currentNode != null) {
                currentNode.setLastHeartbeat(System.currentTimeMillis());
            }
            
            logger.debug("发送心跳: {}", currentNodeId);
        } catch (Exception e) {
            logger.error("发送心跳失败", e);
        }
    }
    
    /**
     * 检查节点健康状态
     */
    private void checkNodeHealth() {
        try {
            long now = System.currentTimeMillis();
            List<String> failedNodes = new ArrayList<>();
            
            for (Map.Entry<String, NodeInfo> entry : clusterNodes.entrySet()) {
                String nodeId = entry.getKey();
                NodeInfo nodeInfo = entry.getValue();
                
                if (now - nodeInfo.getLastHeartbeat() > failoverTimeoutMs) {
                    failedNodes.add(nodeId);
                    nodeInfo.setStatus(NodeStatus.FAILED);
                    activeNodes.remove(nodeId);
                    
                    logger.warn("检测到节点故障: {}", nodeId);
                }
            }
            
            // 处理故障节点
            for (String failedNodeId : failedNodes) {
                handleNodeFailure(failedNodeId);
            }
            
        } catch (Exception e) {
            logger.error("节点健康检查失败", e);
        }
    }
    
    /**
     * 处理节点故障
     */
    private void handleNodeFailure(String failedNodeId) {
        // 如果故障的是主节点，触发故障转移
        if (failedNodeId.equals(primaryNodeId.get())) {
            triggerFailover();
        }
        
        // 重新分配故障节点的数据
        redistributeFailedNodeData(failedNodeId);
    }
    
    /**
     * 触发故障转移
     */
    private void triggerFailover() {
        failoverExecutor.submit(() -> {
            try {
                logger.warn("开始故障转移流程");
                
                // 选举新的主节点
                String newPrimaryId = electNewPrimary();
                if (newPrimaryId != null) {
                    primaryNodeId.set(newPrimaryId);
                    isPrimaryNode.set(newPrimaryId.equals(getCurrentNodeId()));
                    
                    failoverCount.incrementAndGet();
                    logger.info("故障转移完成，新主节点: {}", newPrimaryId);
                } else {
                    logger.error("故障转移失败：无法选举新主节点");
                    clusterState.set(ClusterState.DEGRADED);
                }
                
            } catch (Exception e) {
                logger.error("故障转移过程中发生错误", e);
                clusterState.set(ClusterState.FAILED);
            }
        });
    }
    
    /**
     * 选举新主节点
     */
    private String electNewPrimary() {
        // 简单的选举算法：选择最早加入且活跃的节点
        return activeNodes.stream()
            .filter(nodeId -> {
                NodeInfo nodeInfo = clusterNodes.get(nodeId);
                return nodeInfo != null && nodeInfo.getStatus() == NodeStatus.ACTIVE;
            })
            .min((n1, n2) -> {
                NodeInfo info1 = clusterNodes.get(n1);
                NodeInfo info2 = clusterNodes.get(n2);
                return Long.compare(info1.getJoinTime(), info2.getJoinTime());
            })
            .orElse(null);
    }
    
    /**
     * 重新分配故障节点数据
     */
    private void redistributeFailedNodeData(String failedNodeId) {
        replicationExecutor.submit(() -> {
            try {
                logger.info("开始重新分配故障节点 {} 的数据", failedNodeId);
                
                // 这里应该实现具体的数据重分配逻辑
                // 例如：将故障节点的数据副本分配给其他活跃节点
                
                logger.info("故障节点 {} 的数据重分配完成", failedNodeId);
            } catch (Exception e) {
                logger.error("数据重分配失败", e);
            }
        });
    }
    
    /**
     * 执行数据复制
     */
    private void performDataReplication() {
        try {
            if (!isPrimaryNode.get()) {
                return; // 只有主节点执行数据复制
            }
            
            // 检查复制状态
            for (String nodeId : activeNodes) {
                if (!nodeId.equals(getCurrentNodeId())) {
                    ReplicationStatus status = replicationStatus.computeIfAbsent(nodeId, 
                        k -> new ReplicationStatus(k, System.currentTimeMillis()));
                    
                    // 执行数据同步
                    syncDataToNode(nodeId, status);
                }
            }
            
            dataReplicationCount.incrementAndGet();
            
        } catch (Exception e) {
            logger.error("数据复制失败", e);
        }
    }
    
    /**
     * 同步数据到指定节点
     */
    private void syncDataToNode(String nodeId, ReplicationStatus status) {
        try {
            // 这里应该实现具体的数据同步逻辑
            status.setLastSyncTime(System.currentTimeMillis());
            status.setSyncStatus("SUCCESS");
            
            logger.debug("数据同步到节点 {} 完成", nodeId);
        } catch (Exception e) {
            status.setSyncStatus("FAILED");
            logger.error("数据同步到节点 {} 失败", nodeId, e);
        }
    }
    
    /**
     * 执行备份
     */
    private void performBackup() {
        try {
            if (!isPrimaryNode.get()) {
                return; // 只有主节点执行备份
            }
            
            logger.info("开始执行数据备份");
            
            // 创建备份记录
            BackupRecord backup = new BackupRecord(
                "backup-" + System.currentTimeMillis(),
                System.currentTimeMillis(),
                BackupType.FULL,
                BackupStatus.IN_PROGRESS
            );
            
            backupHistory.add(backup);
            
            // 执行实际备份操作
            boolean success = executeBackupOperation(backup);
            
            backup.setStatus(success ? BackupStatus.COMPLETED : BackupStatus.FAILED);
            backup.setCompletionTime(System.currentTimeMillis());
            
            backupOperations.incrementAndGet();
            
            // 清理旧备份记录
            cleanupOldBackups();
            
            logger.info("数据备份完成，状态: {}", backup.getStatus());
            
        } catch (Exception e) {
            logger.error("数据备份失败", e);
        }
    }
    
    /**
     * 执行备份操作
     */
    private boolean executeBackupOperation(BackupRecord backup) {
        try {
            logger.info("开始执行备份操作: {}", backup.getBackupId());

            // 1. 创建备份目录
            String backupDir = "backup/" + backup.getBackupId();
            java.nio.file.Path backupPath = java.nio.file.Paths.get(backupDir);
            java.nio.file.Files.createDirectories(backupPath);

            // 2. 备份集群配置
            backupClusterConfiguration(backupPath);

            // 3. 备份节点状态
            backupNodeStates(backupPath);

            // 4. 备份复制状态
            backupReplicationStatus(backupPath);

            // 5. 创建备份元数据
            createBackupMetadata(backupPath, backup);

            logger.info("备份操作完成: {}", backup.getBackupId());
            return true;

        } catch (Exception e) {
            logger.error("备份操作失败: " + backup.getBackupId(), e);
            return false;
        }
    }

    /**
     * 备份集群配置
     */
    private void backupClusterConfiguration(java.nio.file.Path backupPath) throws Exception {
        Map<String, Object> config = new HashMap<>();
        config.put("heartbeatInterval", heartbeatIntervalMs);
        config.put("failoverTimeout", failoverTimeoutMs);
        config.put("replicationFactor", replicationFactor);
        config.put("backupInterval", backupIntervalMs);
        config.put("primaryNodeId", primaryNodeId.get());
        config.put("clusterState", clusterState.get().toString());

        String configJson = convertToJson(config);
        java.nio.file.Files.write(backupPath.resolve("cluster-config.json"),
            configJson.getBytes(java.nio.charset.StandardCharsets.UTF_8));
    }

    /**
     * 备份节点状态
     */
    private void backupNodeStates(java.nio.file.Path backupPath) throws Exception {
        List<Map<String, Object>> nodeStates = new ArrayList<>();
        for (Map.Entry<String, NodeInfo> entry : clusterNodes.entrySet()) {
            NodeInfo nodeInfo = entry.getValue();
            Map<String, Object> nodeState = new HashMap<>();
            nodeState.put("nodeId", nodeInfo.getNodeId());
            nodeState.put("address", nodeInfo.getAddress());
            nodeState.put("joinTime", nodeInfo.getJoinTime());
            nodeState.put("status", nodeInfo.getStatus().toString());
            nodeState.put("lastHeartbeat", nodeInfo.getLastHeartbeat());
            nodeStates.add(nodeState);
        }

        String nodesJson = convertToJson(nodeStates);
        java.nio.file.Files.write(backupPath.resolve("node-states.json"),
            nodesJson.getBytes(java.nio.charset.StandardCharsets.UTF_8));
    }

    /**
     * 备份复制状态
     */
    private void backupReplicationStatus(java.nio.file.Path backupPath) throws Exception {
        List<Map<String, Object>> replStates = new ArrayList<>();
        for (Map.Entry<String, ReplicationStatus> entry : replicationStatus.entrySet()) {
            ReplicationStatus replStatus = entry.getValue();
            Map<String, Object> replState = new HashMap<>();
            replState.put("nodeId", replStatus.getNodeId());
            replState.put("createdTime", replStatus.getCreatedTime());
            replState.put("lastSyncTime", replStatus.getLastSyncTime());
            replState.put("syncStatus", replStatus.getSyncStatus());
            replStates.add(replState);
        }

        String replJson = convertToJson(replStates);
        java.nio.file.Files.write(backupPath.resolve("replication-status.json"),
            replJson.getBytes(java.nio.charset.StandardCharsets.UTF_8));
    }

    /**
     * 创建备份元数据
     */
    private void createBackupMetadata(java.nio.file.Path backupPath, BackupRecord backup) throws Exception {
        Map<String, Object> metadata = new HashMap<>();
        metadata.put("backupId", backup.getBackupId());
        metadata.put("startTime", backup.getStartTime());
        metadata.put("type", backup.getType().toString());
        metadata.put("version", "1.0.0");
        metadata.put("nodeCount", clusterNodes.size());
        metadata.put("activeNodeCount", activeNodes.size());

        String metadataJson = convertToJson(metadata);
        java.nio.file.Files.write(backupPath.resolve("metadata.json"),
            metadataJson.getBytes(java.nio.charset.StandardCharsets.UTF_8));
    }

    /**
     * 简单的JSON转换（生产环境建议使用专业的JSON库）
     */
    private String convertToJson(Object obj) {
        // 简单的JSON序列化实现
        if (obj instanceof Map) {
            Map<?, ?> map = (Map<?, ?>) obj;
            StringBuilder sb = new StringBuilder("{");
            boolean first = true;
            for (Map.Entry<?, ?> entry : map.entrySet()) {
                if (!first) sb.append(",");
                sb.append("\"").append(entry.getKey()).append("\":");
                sb.append(convertToJson(entry.getValue()));
                first = false;
            }
            sb.append("}");
            return sb.toString();
        } else if (obj instanceof List) {
            List<?> list = (List<?>) obj;
            StringBuilder sb = new StringBuilder("[");
            boolean first = true;
            for (Object item : list) {
                if (!first) sb.append(",");
                sb.append(convertToJson(item));
                first = false;
            }
            sb.append("]");
            return sb.toString();
        } else if (obj instanceof String) {
            return "\"" + obj.toString().replace("\"", "\\\"") + "\"";
        } else {
            return obj.toString();
        }
    }
    
    /**
     * 清理旧备份记录
     */
    private void cleanupOldBackups() {
        if (backupHistory.size() > 100) {
            backupHistory.subList(0, backupHistory.size() - 100).clear();
        }
    }
    
    /**
     * 获取当前节点ID
     */
    private String getCurrentNodeId() {
        // 这里应该返回当前节点的实际ID
        return "node-" + System.getProperty("user.name", "unknown");
    }
    
    /**
     * 获取集群状态
     */
    public ClusterStatus getClusterStatus() {
        return new ClusterStatus(
            clusterState.get(),
            primaryNodeId.get(),
            activeNodes.size(),
            clusterNodes.size(),
            failoverCount.get(),
            dataReplicationCount.get(),
            backupOperations.get(),
            LocalDateTime.now().format(DateTimeFormatter.ISO_LOCAL_DATE_TIME)
        );
    }
    
    /**
     * 关闭高可用性管理器
     */
    public void shutdown() {
        try {
            heartbeatExecutor.shutdown();
            replicationExecutor.shutdown();
            failoverExecutor.shutdown();
            
            if (!heartbeatExecutor.awaitTermination(5, TimeUnit.SECONDS)) {
                heartbeatExecutor.shutdownNow();
            }
            if (!replicationExecutor.awaitTermination(5, TimeUnit.SECONDS)) {
                replicationExecutor.shutdownNow();
            }
            if (!failoverExecutor.awaitTermination(5, TimeUnit.SECONDS)) {
                failoverExecutor.shutdownNow();
            }
            
            logger.info("高可用性架构管理器已关闭");
        } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
            logger.warn("关闭高可用性管理器时被中断", e);
        }
    }
    
    // 枚举和数据类
    public enum ClusterState {
        INITIALIZING, ACTIVE, DEGRADED, FAILED
    }
    
    public enum NodeStatus {
        ACTIVE, FAILED, LEAVING, JOINING
    }
    
    public enum BackupType {
        FULL, INCREMENTAL
    }
    
    public enum BackupStatus {
        IN_PROGRESS, COMPLETED, FAILED
    }
    
    public static class NodeInfo {
        private final String nodeId;
        private final String address;
        private final long joinTime;
        private volatile NodeStatus status;
        private volatile long lastHeartbeat;
        
        public NodeInfo(String nodeId, String address, long joinTime, NodeStatus status) {
            this.nodeId = nodeId;
            this.address = address;
            this.joinTime = joinTime;
            this.status = status;
            this.lastHeartbeat = System.currentTimeMillis();
        }
        
        // Getters and setters
        public String getNodeId() { return nodeId; }
        public String getAddress() { return address; }
        public long getJoinTime() { return joinTime; }
        public NodeStatus getStatus() { return status; }
        public void setStatus(NodeStatus status) { this.status = status; }
        public long getLastHeartbeat() { return lastHeartbeat; }
        public void setLastHeartbeat(long lastHeartbeat) { this.lastHeartbeat = lastHeartbeat; }
    }
    
    public static class ReplicationStatus {
        private final String nodeId;
        private final long createdTime;
        private volatile long lastSyncTime;
        private volatile String syncStatus;
        
        public ReplicationStatus(String nodeId, long createdTime) {
            this.nodeId = nodeId;
            this.createdTime = createdTime;
            this.lastSyncTime = createdTime;
            this.syncStatus = "PENDING";
        }
        
        // Getters and setters
        public String getNodeId() { return nodeId; }
        public long getCreatedTime() { return createdTime; }
        public long getLastSyncTime() { return lastSyncTime; }
        public void setLastSyncTime(long lastSyncTime) { this.lastSyncTime = lastSyncTime; }
        public String getSyncStatus() { return syncStatus; }
        public void setSyncStatus(String syncStatus) { this.syncStatus = syncStatus; }
    }
    
    public static class BackupRecord {
        private final String backupId;
        private final long startTime;
        private final BackupType type;
        private volatile BackupStatus status;
        private volatile long completionTime;
        
        public BackupRecord(String backupId, long startTime, BackupType type, BackupStatus status) {
            this.backupId = backupId;
            this.startTime = startTime;
            this.type = type;
            this.status = status;
        }
        
        // Getters and setters
        public String getBackupId() { return backupId; }
        public long getStartTime() { return startTime; }
        public BackupType getType() { return type; }
        public BackupStatus getStatus() { return status; }
        public void setStatus(BackupStatus status) { this.status = status; }
        public long getCompletionTime() { return completionTime; }
        public void setCompletionTime(long completionTime) { this.completionTime = completionTime; }
    }
    
    public static class ClusterStatus {
        private final ClusterState state;
        private final String primaryNodeId;
        private final int activeNodes;
        private final int totalNodes;
        private final long failoverCount;
        private final long replicationCount;
        private final long backupCount;
        private final String timestamp;
        
        public ClusterStatus(ClusterState state, String primaryNodeId, int activeNodes, int totalNodes,
                           long failoverCount, long replicationCount, long backupCount, String timestamp) {
            this.state = state;
            this.primaryNodeId = primaryNodeId;
            this.activeNodes = activeNodes;
            this.totalNodes = totalNodes;
            this.failoverCount = failoverCount;
            this.replicationCount = replicationCount;
            this.backupCount = backupCount;
            this.timestamp = timestamp;
        }
        
        // Getters
        public ClusterState getState() { return state; }
        public String getPrimaryNodeId() { return primaryNodeId; }
        public int getActiveNodes() { return activeNodes; }
        public int getTotalNodes() { return totalNodes; }
        public long getFailoverCount() { return failoverCount; }
        public long getReplicationCount() { return replicationCount; }
        public long getBackupCount() { return backupCount; }
        public String getTimestamp() { return timestamp; }
    }
}
